keep your multi-rotor safe…

by ycopter | June 20, 2012 | (35) Posted in Tips

Keep your multi-rotor safe…

 

I have been flying multi-rotors for quite a while now and in that time I have collected some advice that I wished I would have known when I started.  Multi-rotors are dynamic and complex flying machines, one minor fault can lead to a crash.

Why read this article: 

 

·         Safety

·         Reduce expense

·         Save time                      in that order…

 

 


General tips:  

·        Get to know how your machine normally flies, any change in performance is telling you there is a problem.  Land and check it out before the crash!

·        Get into the habit of checking the temperature of each motor and ESC on landing.  One that is hotter than the rest is indicating a problem.

·        Make sure the motors and ESCs are running within their design limits.  Overdriving a motor or ESC is not only inefficient, but it will be expensive in the long run.
 

- Please add YOUR experience –

Comment below and I will add your ideas to this article.


 

1.   Motor Wire Fracture

Cause
Vibration causes fatigue failure of the wire.
Solution
Normally fractures before the solder joint to the bullet connector or the ESC wire. 

Secure the joint well before and after the connector by wrapping tape around joint and around the motor arm. I use self-amalgamating tape which is non-adhesive (only sticks to itself).

Some motors are more susceptible to this problem than others. I used RC Timer 2830-14 750KV motors for many hours without a problem, they are a very smooth and powerful motor but the motor wires are thin and relatively fragile.
 

Well supported motor wire joint.
 


Self-amalgamating tape.
 


RC Timer motor.  Smooth and efficient, but weak wires.
 

 

 

 

 
2.   Threaded Joint Failure  

Cause
Vibration
Solution

When assembling your multi-rotor, check all threaded joints are tight and apply non-permanent thread lock to all metal to metal threads.  Check motor grub screws, they hold the motor together but are often hard to spot and are often forgotten.  Balance the props and reduce vibration as much as possible.

  


3.   Low Battery Voltage

Cause
Flying beyond safe flight time.
Solution
Programme your timer for 80% of the maximum run time the battery can sustain. Use battery low voltage alarms and on screen displays to alert low voltage.

 


4.
  
FPV Feed Stops

Cause
Likely to be an intermittent connection into the video transmitter. If you use GoPro live feed out for FPV, be aware that when the GoPro battery is exhausted, the camera switches itself off leaving you with a blank video screen!
Solution
Pay attention to all video leads and joints.  Where possible solder video leads directly onto the video transmitter and other devices. Avoid connectors in the video feed where possible, they can be unreliable.  Keep video leads as short as possible.

 


5.
  
Propeller Failure

Cause
Using damaged or poor quality propellers.
Solution
Use good quality props, paying the extra can save your multi-rotor from an expensive crash.

   


Failed propeller.  This one failed in flight without warning.  It was almost new and had not been crashed or stressed previously. 


Genuine APC next to equivalent lower quality propeller.


6.
  
ESC Failure

Cause
Various causes but most likely is running all ESCs with their BEC wires intact. Excess current or voltage can also cause failure.
Solution
Use reliable ESCs and disconnect the BEC (red cable) from all but one of the ESCs. I use RC Timer and Hobbywing ESCs.

 
An example of a high quality ESC.


7.
  
Elctrical Intereference

Cause
High currents into and out of ESCs generate signifcant noise, which in severe cases can cause servos to loose sync, and receivers to experience reduced range.
Solution
Keep the RC receiver and its leads away from ESCs and high power cables.  Avoid routing receiver cables alongside and in contact with ESCs and their input and output wires.  

 


8.
  
RC Control is Lost

Cause
Flying beyond safe range, interference, poor antenna installation, poorly oriented or sighted TX antenna.
Solution
With multiple causes, the only safe thing to do is to carry out thorough range tests. This articleis a good starting point.  Keep video transmitter antennas and radio control receiver antennas as far apart as possible.  Use frequencies that are less likely to interfere with each other.  Keep the FPV video transmitter power to a minimum, overdriven video transmitters cause widespread and spurious harmonic interference.

 



9.
  
Connector Failure

Cause
Wrong choice of connector for the application, poor installation and wear and tear.
Solution
Any connector can and does fail. Make sure you use the right connector for the job and make sure it is terminated and installed correctly.

Servo leads are particularly vulnerable. The pre terminated ones are better quality, if you need to shorten or extend a lead, do so by soldering the lead.

Male “Deans Type” plugs do wear out. The springs become straight meaning they are not so securely connected from a mechanical and electrical perspective.

 



10.
                    
Solder Joint Failure

Cause
Cold solder joint.
Solution

Use a hotter soldering iron. Use the right type of solder and become expert at soldering. Multi-rotors have many solder joints, anyone of them could fail if not soldered correctly.

 

 


- Please add YOUR experience –

Comment below and I will add your ideas to this article.


 
   

 

 

 

 

COMMENTS

ukbozzy on June 22, 2012
Hi All, I'm in total agreement with the above advise, as a newbie to Tricopters ive had my steep learning curve as we all do and advise such as this is invaluable...The point id like to highlight and what helped me diagnose my recent problem with my tricopter not hovering, is SOLDERING after many many hours and emails back and forth to Ycopter ( Richard ) i checked my solder on all my connections, and even tho they looked good when i did them, they actually had poor connections and with a gentle pull i could break the joints. So my Advise is to check and double check your Solder.. If you are having problems with erratic motors and not flying level no matter what you try.. Then Check your connections.
Thanks again!! Steve
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ycopter on June 22, 2012
ukbozzy, you illustrate the point that just one bad solder joint can cause a crash months later. The safety and success of your flights are pre-determined by quality control on the bench well before the first flight!
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3zuli on June 23, 2012
Great article. I'm sure a lot of newbies (like me) will appreciate this guide. Here are some tings, that could be added:
4. If you have problems with your video (caused by interference from ESC or RC system), you could try using coaxial cable for all the video signals and at least shielded cable with ferrite rings for powering the video equipment. That should make your video system much more noise-proof.
10. Soldering is everything. Learning to avoid cold joints is the key to success. First, use flux. If you don't, the joint will become loose after just a little bit of vibrations or mechanical stress. Second, I see a lot of people using these cheap, <40W mains powered soldering irons. But these usually don't have enough power to heat up the connection fast enough and that (when working with sensitive components) can even lead to damaging the component(s). My advice is to buy a good soldering "gun", rated for 100W. A good soldering iron/gun should melt solder within 3 seconds. Third - solder as quickly as possible, and in multiple steps, if needed. Pre-tin both the (for example) cable and connector, using flux. Then take a bit of solder on the tip of your soldering iron, dip it in flux and finally solder the 2 pieces together. I reccomend to use the "helping hands" tool to hold the connection, while you have your hands free for soldering iron.
Just my 2 cents :)
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ycopter on June 23, 2012
Thanks for the additional detail. Soldering is something you have to get very good at if you build multi-rotors. A typical quadcopter has more than 50 high power soldered joints! Your advice regarding video equipment is helpful, both subjects could really do with an article in their own right.
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Pillip Flop on October 9, 2012
I could have used this information last week when I lost Tx completely due to I think, bad orientation. My quad turned into a dot then diapered over the horizon I found it sometime later sticking out of someone’s roof. Looking back now I know I was rushing too much to get in the air. I did an article about the crash you can hear the change in motor tone when I lost Tx . Some really good knowledge here thanks.
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ycopter on October 10, 2012
Sorry to hear about your misfortune, it happens to all of us, gravity is very unforgiving.
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Nic on June 21, 2012
I haven't yet flown my tricopter, but those advices are exactly the ones that a new tricopter pilot would like to know!

Thanks!
Nic
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ycopter on June 22, 2012
I am glad you appreciate the article, I hope it saves you some time and money!
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Flying on June 21, 2012
For Tricopter flyers: Make sure that servo/other wires are as far away as possible from ESC and motor wires as I have had servos on my tricopters lose sync due to the electrical/magnetic affects these high current wires can have when in use.
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ycopter on June 22, 2012
Hello "Flying". Thanks so much for taking the time to contribute your experience. I am going to embed your advice into the article, but before I do can you confirm what type of radio equipment and servo you were using. Interestingly my Tricopter servo wire runs right alongside the battery and ESC wires, and I have not experienced any problem so far. I wonder if this problem is specific to a particular servo or receiver type?
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Flying on June 23, 2012
http://www.youtube.com/watch?v=ggClau_2jEk
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Flying on June 23, 2012
Hi I am using FrSky receivers and a turnigy-9x transmitter. Specifically I had tucked the servo extensions under the wires that exit the ESC and lead to the motors to try and make my tricopter look neat. I was getting glitches about once or twice a flight and lasted about 4 or 5 seconds in my BMS-385DMAX Digital Servo but I didn't think to much of it. After a while it really started to annoy me so I experimented a bit with different servos and the problem continued. After many servos I found my wire placement to be the problem. After moving the servo cable to the opposite side of the arm I have not had any more GLITCHES and I am still using my original servo to date. After this I made sure to try and isolate by moving them as far away as possible from the ESC's. I really wish someone had told be about the frequency's that ESC's can emit earlier. I new about them but I never thought it could have such an effect that it would cause a servo to lose sync and be uncontrollable.
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ycopter on June 23, 2012
Thanks for the additional detail. I have updated the article, see item number 7.
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colorex on June 22, 2012
Excellent article! It's really well formatted - and well written. This is the kind of content we like on FliteTest!

My personal experience, I'm currently grounded because a grub screw for a motor got lost in mid-air. I now need a new DT750. Should have used Loctite.
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ycopter on June 22, 2012
Good point, these grub screws are hidden away and often forgotten. I have just located them on my new NTM motors and will be checking to see if they are tight and adding some thread lock!
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ycopter on June 22, 2012
I have edited the article to mention motor grub screws.
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colorex on June 22, 2012
Great! I hope it will save someone a crash!
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rcjoseb on October 15, 2012
I have a few tips:

Never use prop savers on multirotors as you are basically hanging the weight of the multirotor on rubber bands. Great for planes though.

If there is a gap between male and female bullet connectors, use tape, i.e. 100 rubber tape, to cover the joints so they cannot short out if touching another connector or metal.

Secure the main lipo battery with two velcro straps. One going from top to bottom and the other left to right. This way it will not slide out in mid flight.

Wheb flying FPV, keep the antenna as close to the video receiver as possible. Never extend the antenna cable. For better reception, raise the FPV receiver and antenna as high as possible.

If possible, incorporate folding arms in to your multirotor design. Upon crashing, the arms will bend back/forward which minimizes damage.

Zipties are your best friend.

Program ESC's for multirotors as ESC's are usually designed/pre-programmed for airplanes:

Brake Setting = OFF
Battery Type = NiMh
Low Voltage Protection = SOFT CUTOFF
Low Voltage Protection Threshold (if available) = OFF or 0
Startup Mode = NORMAL
Timing = HIGH
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ycopter on October 16, 2012
rchoseb, thanks for sharing your experience. I hope you didn’t have to suffer too many crashes to discover this! Sharing this knowledge helps us all; I used your original KK firmware flash video to flash my first KK board...
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Gart on June 26, 2012
That great, this article will probably help me soon enough, i begin to think about getting into this.

Thx
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ycopter on July 13, 2012
Thanks, look forward to seeing your multi-rotor flying!
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Deeleins on December 1, 2013
Thanks for the article ycopter- I'll be binding up my motor wires now. One tip from me would be -like with planes, the CG - I find that it makes quite a difference to how my tri flies. And my other one for people learning to fly would be (heard from a heli pilot) : planes you learn to fly from 2 mistakes high, copters you learn to fly from the ground up. I have had lots of minor crashes with the tri near the ground- no damage. As a noob there was no way I was ever going to recover correctly from incorrect stick movements so being near the ground really kept the damage to the occasional prop.
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ycopter on December 8, 2013
Deeleins, thanks for adding your experience to this article, when I have time I will update the article to give some tips on CG and initial flights.
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keep your multi-rotor safe&hellip;